more info from aspinkney, interior damp


Postby c-shields » Tue Jan 13, 2009 11:16 pm

Live in mid terrace, exterior walls and party wall to left are dry. Party wall to right and internal dividing wall are damp to height of 75cm. All walls on the ground floor have had a damp course. The guarentee was invalid due to the damp being on a party wall and the man who carried out the work can not be traced by us or the manufacturer of the damp product. As we have the plans and guarentee we can clearly see this was carried out, when we removed a section of plaster from the damp wall we could see the drill holes. We have no mould growing or condensation or other signs of damp, the walls do not feel wet yet the damp detector we bought (and that of the surveyor provided by our new mortgage company) found the walls to be damp. Would another course of drilling and injecting be best or due to this failing in the past would you recommend another product, I hear they can be sprayed or sealed with a bitchimen type sealer?
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Postby the specialist » Wed Jan 14, 2009 10:27 am

Hi

You say there are no visible signs of dampness and the only indication of damp is from an electrical moisture meter (damp meter).

The first point to note is that under the guidlines of the bwpda an electrical moisture meter can not be used to confirm the effectiveness of a remedil damp proof course.

This is because when a wall has been subjected to rising damp it has had moisture from the ground rising up the wall. This moisture contains salts from the ground mainly chlorides, nitrates and sulphates.

Because some salts are hygroscopic (absorb moisture from the air) they can obviously draw moisture from the room and dampen the plaster. This in turn will show a higher reading in the wall plaster.

I would suggest that there may be salts present in the plaster (which if re-plastering was carried out may have been the wrong plaster)

If there is no damage occurring I would leave well alone.

What you can do is insert the probes of the damp meter into the timber skirting board in this area and see what reading you get. If the moisture content is low then everything is probably ok. If high 16% or upwards then let me know and I will give you further advise.

Did you know that moisture meters work on w.m.e. - wood moisture equivalent. That is what they were designed for. They only give a trained person an indication of what is happening. Everything has some moisture in it but often it is low enough not to cause any problems or warrant the spending of your hard earned money on.

Its a pity that the majority of building surveyors don't actuall know how to use one properly.

Hope this is of help.

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Postby c-shields » Wed Jan 14, 2009 9:02 pm

plaster has been hacked off about 3 ft up the wall the reading is off the brick work
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Postby Paul B » Thu Jan 15, 2009 12:33 pm

I read thsi with interest, and I am hoping it is similar to a problem I have and may threfore give me cause for LESS stress about a damp area I have.

We had treatment on a dwarf wall in a Victorian house, ie dpc injection, re-plastered, but an area of the wall on one side was replastered poorly and a moisture meter reads moisture on the plaster surface (now painted) - there seems no tide mark, or flaking yet in more moist weather (i.e warmer air) the meter reads moisture. When the air is very cold (i.e. over Xmas in cold weather) no reading! So this to me suggests hygroscopic salt contamination of an area of the new plaster. As no spoiling I am inclined to just leave it. The skirting boards do indicate mositure in them, not much, and again no spoiling - so again inclined to just leave.

i do have some salt neutraliser solution - would it be an idea for me to apply some to the painted wall in the area which seems to have presence of these salts from the old rising damp??

Any thoughts very gratefull received!

P
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Postby the specialist » Thu Jan 15, 2009 1:42 pm

Ok - so the plaster is gone. All my previous comments still apply. If you can see the bricks and they look dry then they should be. If they look wet then the dpc isn't working. We use damp meters on plaster because we cant see the bricks under normal circumstances. You could always get a speedy test (calcium carbide) carried out on the brick to check the actual moistute content in the wall as opposed to the surface.
one other thing to check is as follows.

Is your ground floor level the same as that of the adjoining property. If not you will have split dpc's. If your property is lower than next door their dpc will be higher than yours, which will allow dampness to track back above your dpc.

I'm only trying to help and by the way I am C.S.R.T. qualified.
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Postby the specialist » Thu Jan 15, 2009 7:23 pm

Hi Paul b

To be perfectly honest I have never tried using a salt neutraliser after plastering, (its usually used before plastering. We also use salt retardant additives in our plastering system) so I can't really say. However I dont see how it can do any harm - although you probably would need to remove the paint first.

How long ago was your plastering done, how soon after did you paint it and what kind of paint did you use?

Also what was the actual moisture reading in the skirting board?

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Postby Paul B » Fri Jan 16, 2009 10:22 am

Thanks for your reply Aiden.

The work was done way back late August/early Sept. I think that the re-decorating may have been done a little too soon, not letting all of the plaster dry out entirely - the painting was done within a week or so of the new dpc and re-plaster work.

They used an undercoat mist, then a bathroom paint (easy wipe stuff) - the moisture meter only gives a reading on the surface, I don't really want to dig the pins into the wall, and it is in a very localised area - it is also patchy in reading, certainly no damp feeling, but the finish, as I said at this point, in the plastering is poor - I think as the wall is small and not very visible decoratively the plasterer cut corners on that side of the wall, and didn;t do the best job. Anyway, in warmer air/moist air conditions, the moisture meter will give a reading on the surface, soon as it turns cold in the air, no reading!

As for the skirting, again I only have a basic moisure meter - and in parts it read 2 out of 3 red dots on the skirting, but there is no flaking paint or cracking wood at present, and all very minimal.

Since living in the property this small rear internal wall has been a stress for me - I worry it os something really bad, but every builder, damp proof person has said it really is not a big problem worth worrying about so much.

I haven't applied the salt neutraliser, as I don;t want to make anything worse, it may just be best left really. Not sure what to do really. Worst case is to have all the new plaster hacked off again and re-done, but I'd rather not to be honest if can be avoided, and I know my wife would rather I just shut up about it!!!!

Any thoughts Aiden?
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Postby the specialist » Sat Jan 17, 2009 6:18 pm

Hi Paulb

I think you should relax and do nothing for now. Keep your eye on the skirting for signs of shrinkage.

The basic rule with moisture levels is that if they are not causing damage to timber, plaster or decor then it is not justifiable to spend money on it.

So keep your cash for now.

Good luck.

Aidan
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Postby Paul B » Mon Jan 19, 2009 9:42 am

Thanks Aidan, that is reassuring. Damp is one of those things that I do really worry about, but bearing in mind I have done everything possible I can to help remedy the damp in this area, and that the decoration isn;t spoiling or the wood showing any shrinkage or flaking, maybe you are right.

Maybe I should just get rid of my damp meter, and stop checking, the moisture level changes daily depending on the conditions, and as it doesn;t seem to be spreading, or getting worse, or indeed showing any signs of deteriation in the condition of the wall then I should be well advised to leave well alone.

Thanks very much for your advice, I am not the most confident DIY-er when it comes to DAMP!!!!

P
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Postby TheDoctor5 » Fri Jan 30, 2009 10:18 am

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